A communication network is a collection of nodes interconnected by communication links and segments for transporting information (e.g., data) between the nodes. The nodes may include intermediate nodes, such as routers and switches, and end nodes, such as personal computers, telephones, personal digital assistants (PDAs), video units and the like. The intermediate nodes are typically forward information in the network between the end nodes. The end nodes typically act as origination and destination points for the information.
Many types of communication networks are available, with the types ranging from local area networks (LANs) to wide area networks (WANs). LANs typically connect nodes over dedicated private communications links located in the same general physical location, such as a building or campus. WANs, on the other hand, typically connect large numbers of geographically dispersed nodes over long-distance communications links, such as common carrier telephone lines. The Internet is an example of a WAN that connects networks throughout the world, providing global communication between nodes on various networks.
The nodes typically communicate over the network by exchanging discrete frames or packets of data according to predefined protocols, such as the Transmission Control Protocol/Internet Protocol (TCP/IP). In this context, a protocol consists of a set of rules defining how the nodes interact with each other.
Some communication networks utilize communication sessions to communicate information, such as video and/or audio information, between users in the network. A communication session is a transaction in which information is exchanged between two or more parties in a communication network. The parties may be, e.g., users, computer systems, network devices (e.g., routers, switches), telephones and the like. An example of a communication session is a telephone call between a plurality of parties in which audio information is exchanged between the parties. Another example of a communication session is a videoconference between a plurality of parties where video and voice may be exchanged between the parties. Communication sessions are typically established between a calling party and a called party. A calling party is a party that typically initiates the session by e.g., placing a call to the called party. The called party is the party that is being called by the calling party.
A secure communication session is a session in which information is exchanged in the session in a secure manner in order to avoid unauthorized reception of cleartext communications, e.g., eavesdropping. Encryption is often employed to secure the information. One cryptography technique that may be used to encrypt information in a secure communication session is “public key” cryptography. Here, each party in the secure communication session is associated with a pair of cryptographic keys, designated as a public key and private key, that are used to secure information. A party's public key is made public to other parties in the session and is used by those parties to encrypt information intended for the party. A party's private key is kept private by the party (i.e., not disclosed to others) and is used by the party to decrypt information that was encrypted using the party's public key. Eavesdropping is avoided using this scheme because the private key must be known in order to decrypt the received encrypted information.
Some secure communication systems employ special equipment to perform encryption. For example, some secure communication systems employ special telephones that are configured to encrypt/decrypt information carried in a secure communication session. In a typical arrangement, as a party speaks into the telephone, the telephone equipment digitizes party's speech, encrypts the digitized speech and transfers the encrypted digitized speech to another party. The other party's telephone receives the encrypted digitized speech, decrypts it to reveal the original digitized speech and converts the digitized speech to audio signals that are heard by the other party.